With the recent spread of portable devices such as mobile phones, smart phones, and tablet terminals, need for a pedestrian navigation system has increased and demand for an azimuth measuring device that measures a current position and a travel direction of a pedestrian and that can be mounted on portable devices has increased.
Devices such as a game controller, a television remote controller, or a digital camera have been progressively equipped with sensor components for measuring a physical quantity, such as a geomagnetic sensor or an acceleration sensor for the purpose of providing a function corresponding to a user's taste or state.
In general, plural components are arranged in the electronic devices and components giving an influence to the sensor components are often used.
For example, in a geomagnetic sensor, ideally-measured geomagnetic values are generally distributed in a spherical shape centered on an origin (geomagnetic measurement sphere). However, due to influences of magnetic components present around the measuring device, the measured geomagnetic values are not actually distributed in a spherical shape centered on an origin.
FIG. 1 is a diagram schematically illustrating a hard magnetic material effect (Hard-Iron Effect). In FIG. 1, a two-dimensional shape is illustrated for the purpose of simplification. (hereinafter, a two-dimensional shape is illustrated in the drawings for the purpose of simplification but the same is true of three or more dimensions.) When the magnetic component giving an influence to a measuring device is a component exhibiting hard magnetism such as a magnet, measured geomagnetic values have offsets and are distributed in a spherical shape centered on a vector corresponding to an offset magnetic field.
FIG. 2 is a diagram schematically illustrating a soft magnetic material effect (Soft-Iron Effect). When the magnetic component giving an influence to a measuring device is a component exhibiting soft magnetism, such as iron, the measured geomagnetic values are deformed and distributed in an ellipsoidal shape.
Since the influence of the offset magnetic field or the deformation of the distribution shape causes an azimuth error, it is necessary to correct the influences thereof so as to obtain a correct azimuth.
As a method of correcting an influence of a hard magnetic material, for example, PTL 1 discloses an azimuth measuring device and an azimuth measuring method using geomagnetism detecting means and more particularly an azimuth measuring device and an azimuth measuring method that are suitable for correcting an offset of a magnetic sensor, in which an offset obtained when physical quantity data is distributed on a spherical surface is calculated.
As a method of correcting an influence of a soft magnetic material, for example, PTL 2 discloses a fundamental computation technique for correcting obtained ellipsoidal data so as to be distributed in a spherical shape when physical quantity data to be originally distributed in a spherical shape is distributed in an ellipsoidal shape.